[mrtg] MRTG Script error

[SYED JAHANZAiB ~!~ AA Internet Cable.Network Services]

I am facing a littile problem in creating MRTG Graph for Disk I/O perfromance.
I created script to collect read/write data by thie following script.
 
################################
#disk.sh
#!/bin/bash
Kbr=`iostat -x |grep sda | awk '{print $7}' |sed "s/[.]//"`
Kbw=`iostat -x |grep sda | awk '{print $6}' |sed "s/[.]//"`
echo $Kbr
echo $Kbw
################################
If I run disk.sh, it shows me following result which is ok

429
26

My disk.cfg is as follows...
################################
Target[disk]: `/usr/local/mrtg-2/bin/disk.sh`
Title[disk]: Disk HDA I/O Utilization Report
#Unscaled[disk]: dwym
MaxBytes[disk]: 10240000
PageTop[disk]: Disk I/O Utilization Report
kmg[disk]: KB,MB,GB
LegendI[disk]: Disk I/O KBread/sec
LegendO[disk]: Disk I/O KBwrite/sec
Legend1[disk]: Disk I/O KBread/sec
Legend2[disk]: Disk I/O KBwrite/sec
YLegend[disk]: Megabytes
ShortLegend[disk]: &
Options[disk]: growright,gauge,nopercent
#################################
 
But when i set it in MRTG , it shows me follwing error and donot updatedisk Graph.
 
##################
 
2008-04-21 17:04:02 -- Started mrtg with config '/usr/local/mrtg-2/bin/mrtg.cfg'

2008-04-21 17:04:38 -- 2008-04-21 17:04:02: WARNING: Problem with External get '/usr/local/mrtg-2/bin/disk.sh':
   Expected a Number for 'in' but got ''
 
2008-04-21 17:04:38 -- 2008-04-21 17:04:02: WARNING: Problem with External get '/usr/local/mrtg-2/bin/disk.sh':
   Expected a Number for 'out' but got ''
 
2008-04-21 17:04:38 -- 2008-04-21 17:04:38: ERROR: Target[disk][_IN_] ' $target->[47]{$mode} ' did not eval into defined data

2008-04-21 17:04:38 -- 2008-04-21 17:04:38: ERROR: Target[disk][_OUT_] ' $target->[47]{$mode} ' did not eval into defined data

#############################
 
What could be the error ???
 
Regards,
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